Containers used, for example, for packaging liquid products, often include a container body that terminates at the top end with a radially outwardly, downwardly, and inwardly directed curl. For internally pressurized containers (e.g., aerosol containers), for example, the purpose of the curl is to support the valve cup and a gasket to seal against and strengthen the area where a connection is made to the valve cup.
Conventional curls and curling processes have been found to have several disadvantages. For example, forming a curl with a large radius presents a greater opportunity for the material to split as the material is being formed outward from its original state. This is particularly true if compression was previously applied to the material during prior necking or forming operations and/or where the container includes a welded seam along the axis of the cylindrical body of the container and the weld is harder than the base material (e.g., in aerosol containers).
It would be desirable to have methods and apparatuses that address these deficiencies.